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The Rochdale Canal runs for 33 miles between Manchester and Sowerby Bridge in West Yorkshire, UK. In Sowerby Bridge it connects with the Calder and Hebble Navigation. In Manchester it connects with the Ashton and Bridgewater Canals.

The canal was opened between Sowerby Bridge and Todmorden and from Manchester to Rochdale in 1799 and between Todmorden and Rochdale in 1805. Most of the canal was closed in 1952. Restoration work began in late 1980s and by 1996 the canal was opened to navigation once again between Sowerby Bridge and the summit level. The canal was re-opened to navigation along its entire length in July 2002 and forms part of the South Pennine Ring.

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Listed buildings and structures are officially designated as being of special architectural, historical or cultural significance. There are over half a million listed structures in the United Kingdom, covered by around 375,000 listings.
Listed status is more commonly associated with buildings or groups of buildings, however it can cover many other structures, including bridges, headstones, steps, ponds, monuments, walls, phone boxes, wrecks, parks, and heritage sites, and in more recent times a road crossing (Abbey Road) and graffiti art (Banksy 'Spy-booth') have been included.

In England and Wales there are three main listing designations;
Grade I (2.5%) - exceptional interest, sometimes considered to be internationally important.
Grade II* (5.5%) - particularly important buildings of more than special interest.
Grade II (92%) - nationally important and of special interest.

There are also locally listed structures (at the discretion of local authorities) using A, B and C designations.

In Scotland three classifications are also used but the criteria are different. There are around 47,500 Listed buildings.
Category A (8%)- generally equivalent to Grade I and II* in England and Wales
Category B (51%)- this appears generally to cover the ground of Grade II, recognising national importance.
Category C (41%)- buildings of local importance, probably with some overlap with English Grade II.

In Northern Ireland the criteria are similar to Scotland, but the classifications are:
Grade A (2.3%)
Grade B+ (4.7%)
Grade B (93%)

Read more at Wikipedia Link